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Psychiatry has never been able to cope satisfactorily with the difficult question of differential diagnosis. It has been thought that clinical neurophysiology, through the analysis of P300 impairments, could solve this problem. But a lack of sensitivity and of specificity precludes its clinical use. We propose that the use of an emotional oddball, using crossmodal (audio-visual) stimuli, could solve some of these problems. As psychiatric patients usually show some deficits in emotional information processing, investigating them with ERP could elicit different patterns of P300 and prior brain waves. We hope, trough this new design, to be able to differentiate between normal and pathological, and to discriminate more accurately patients with different pathological processes. [ABSTRACT FROM AUTHOR]

It is customary to consider that a purely sensory and painful neuropathy accompanied by normal electroneuromyographic examination may be or must be a small fiber neuropathy. This leads to perform specific tests, such as measuring the intra-epidermal nerve fiber density on skin biopsy or neurophysiological tests, such as evoked potentials to noxious stimuli (laser) or quantification of thermal sensory thresholds. However, these tests are only sensitive to the loss of small fibers (A-delta and C), which does not reflect the mechanisms responsible for peripheral neuropathic pain. Selective loss of small sensory fibers inherently generates a sensory deficit that does not necessarily present a painful character. Also, assigning the cause of a painful neuropathy to a small fiber neuropathy has no pathophysiological sense, although there are indirect links between these two conditions. In fact, it is not possible to explain univocally peripheral neuropathic pain, which reflects complex and diverse mechanisms, involving different types of nerve fibers. In this context, the clinical and laboratory approach must be improved to better understand the underlying mechanisms. It is imperative to interpret the data provided by laboratory tests and to correlate these data to the clinical signs and symptoms presented by the patients. Thus, one must go beyond many a priori and misinterpretations that unfortunately exist in this area at present and are not based on any solid pathophysiological basis., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)